1. Field of the Invention
The present invention relates to robotic devices and methods. In particular, the invention relates to systems and methods for orienting an end-effector about two axes intersecting at a fixed geometric point located distally, materializing a pivot point or a Remote Center of Motion (RCM).
2. Description of the Related Art
In robotics the pivot point and kinematic principle used is commonly referred to as the Remote Center of Motion. Systems and methods for orienting parts, tools, and instruments about a RCM point distal to the mechanism are well known. For example, see U.S. Pat. Nos. 5,397,323, 5,515,478, 5,630,431, 5,817,084, 5,907,664, 6,047,610, and 6,246,200, the entire contents of each are incorporated herein by reference.
The RCM principle is commonly used in freehand surgical practice. In robotic assisted surgery, several mechanisms implementing the RCM principle have also been developed. The present invention is a new type of RCM mechanism possessing unlimited rotations, with no kinematic singularities, and adjustable RCM point.
U.S. Pat. No. 4,098,001 to Watson introduced the precursor of the RCM, the Remote Center of Compliance (RCC) principle, which was derived for industrial robot applications of peg-in-hole insertions. RCC mechanisms give rotational and translational compliance for the “peg” at the insertion point into the “hole” so that the robot can perform the assembly operation in case of misalignment. Commonly, the motion is restricted to a narrow region and it is passive.
U.S. Pat. No. 4,098,001 describes a passive 3-D n-bar linkage RCC mechanism for part assembly operations. A flurry of inventions by Watson's collaborators (see U.S. Pat. Nos. 4,409,736, 4,477,975, 4,556,203, and 4,537,557; Nevins J, (1981): “Systems analysis and experimental study advance the art of assembly automation”, Assembly Automation, vol. 1, no.4 p. 186–9; Masamune K, Patriciu A, Stoianovici D, Susil R, Taylor R E, Fichtinger G, Kavoussi L R, Anderson J, Sakurna I, Dohi T, (1999), “Development of CT-PAKY frame system—CT image guided Needle puncturing manipulator and a single slice registration for urological surgery”, Proc. 8th annual meeting of JSCAS, Kyoto 1999:89–90) describe a number of other solutions employ rigid and elastic linkage mechanisms, both passive and active, to achieve RCC motion for manufacturing assembly operations. All of these mechanisms have limited range of angular motion as a result of their linkage designs. Currently, numerous passive types of 3-D linkage RCC devices are commercially available, for example from ATI Industrial Automation (http://www.ati-la.com/another.htm), RISTEC (http)://wyvw.ristec.com/rcc.htm), and PFA, Inc. (http)://www.pfa-inc.com/rccfront.html). The RCC mechanism only allows rotational, pivoting motion about the fulcrum point, it is performed on a larger range, and it is normally actuated.
U.S. Pat. No. 5,397,323 to Taylor et al. introduced the RCM principle with the invention of the “Remote Center-of-Motion Robot for Surgery”. The invention was implemented on an LABS robot developed at IBM, which uses a pivot RCM point proximal to the patient but distal from the robotic mechanism. See also U.S. Pat. No. 5,630,431. In the Taylor systems, the first axis of rotation points into the RCM, and the second axis is materialized by a parallelogram mechanism implemented by two coupled parallel linkages of rigid bars and cylindrical joints. The two axes of the RCM are orthogonal, and the mechanism operated around an upright initial (zero) direction.
In U.S. Pat. No. 5,630,431, the robot uses two concentric goniometer arcs of normal relative orientation connected in series. See also Cutting C B, Bookstein F L, Taylor R H, (1996): “Applications of Simulation, Morphometrics and Robotics in Craniofacial Surgery, in Computer-Integrated Surgery,” MIT Press 1996: Cambridge, Mass. p. 641–662; 37. Taylor R E, (1991): “A Model-Based Optimal Planning and Execution System with Active Sensing and Passive Manipulation for Augmentation of Human Precision in Computer-integrated Surgery”, Second Int. Symposium on Experimental Robotics, Toulouse, France; Taylor R H, (1992): “Augmentation of Human Precision in Computer-Integrated Surgery”, Innovation et Technologie en Biologie et Medicine, 13(4 (special issue on computer assisted surgery)): p. 450–459; and Taylor R H., (1992): “A Passive/Active Manipulation System for Surgical Augmentation”, First Int. Workshop on Mechatronics in Medicine, Malaga, Spain. The RCM point is located at the common center of the guides, which is located distal from the mechanism. The two directions of rotation are orthogonal. The location of the pivot point is locked by the architecture of the mechanism, and the robot could only be operated around an upright initial orientation.
In 1998, Jensen modified Taylor's initial design in U.S. Pat. No. 5,817,084. The robot in that patent replaced the parallel linkage of bars at the base of the parallelogram mechanism with a belt drive (“Flexible Drive”). The mechanism was implemented on an SRI robot for laparoscopy. See Cornum R L, Bowersox J C: Telepresence: a 21st century interface for urologic surgery. J Urol. 1996; 155 (Supp 5): 489A. Abstract 715. Although Jensen realized the advantage of replacing the parallel linkage with a continuous transmission, he did not fully eliminate its use. For this reason, his mechanism inherited certain poor characteristics of the Taylor system: limited range of motion around an upward zero, unequal stiffness at different positions. This prior art RCM system is also unadjustable and has axes that are orthogonal.
It is known that the RCM point can be defined and mechanically locked by the kinematics of the mechanism, or can be arbitrarily chosen and implemented with a high degrees-of-freedom (DOF) mechanism under coordinated joint control. Almost any high mobility robot can be programmed to perform such a task. U.S. Pat. No. 6,047,610 describes an example. This approach has advantages of pivot flexibility, increased maneuverability, and overall versatility. However, these mechanisms are unsafe for surgical applications. Mechanical RCMs are safer due to their reduced DOF, decoupled motion and locked pivot features.
Between 1996 and 1999 Wang et al. reported a series of ten inventions entitled “Automated Endoscope System for Optimal Positioning” [42,43] or similar for the AESOP robot (Computer Motion, Inc., Goleta, Calif., http://www.computermotion.com/). The last two joints of the AESOP robot are passive and rotary with intersecting axes. The intersection of these axes is neither remote from the mechanism nor located at the laparoscopic port level. The laparoscopic instrument occupies a free orientation between the end of the robot and the laparoscopic entry port. The AESOP is not a genuine RCM mechanism, but rather, a floating RCM, which provides a safe way of pivoting the laparoscope.
More recent advancements in the RCM field are related to the daVinci robot (Intuitive Surgical, Inc., Mountain View, Calif., http://www.intusurg.com/). See U.S. Pat. No. 6,246,200. This system comprises a bilateral surgical robot and a camera holder performing laparoscopic tasks under direct control of a surgeon located at a command console. Both the robot and the surgeon's console use a version of an RCM mechanism. The RCM mechanism is a very elegant, but rather massive version of the original Taylor RCM. Like Jensen, Intuitive Surgical modified the base linkage of the parallelogram mechanism in order to accommodate the drive-of the additional cable driven DOF. Kinematically, daVinci has the same capabilities as Taylor's LARS robot.
With very few exceptions, the prior art RCM mechanical devices for use in surgical applications are either goniometer arc systems or are variations on the Taylor design, from the original LARS robot to the newest and highly sophisticated daVinci. The prior art devices each have limitations that beg improvement. In particular, rigid linkage RCM designs have limited range of motion.
Thus, there is a need for new and improved image based target guiding systems and methods that take advantage of commonly available imaging technology and solve the problems with the prior art.